Adding new LWC Version called SearchGiphyLwc

[dseligson]

This commit appends an LWC component called "SearchGiphyLwc" which behaves nearly the same as the still existing SearchGiphy aura component. Either component may still be used with the exact same setup steps. For the updated experience, after installing the source code, edit the GIFter Home page and replace the existing SearchGiphy component with the new SearchGiphyLwc component.

Additional enhancements include:

1. Spinner is displayed while Chatter Post is created
2. fetch api is used instead of jQuery $.getJSON()
3. Error Toasts are presented if Giphy Search fails or Chatter Post fails.

[dseligson]

Note that there is a Trailhead project which uses the GIFter code base and two of the Steps in the project need API version numbers to be updated from "43.0" to "45.0"
In the instructions where the sfdx-project.json file is displayed, the sourceApiVersion is shown as "43.0".
This must be increased to "45.0" so that the lwc components may be installed.

• Change "43.0" to "45.0" in TWO places in this project
  https://trailhead.salesforce.com/content/learn/projects/quick-start-unlocked-packages/create-test-and-deploy-your-unlocked-package

• Change "43.0" to "45.0" in ONE place in this project:
  https://trailhead.salesforce.com/content/learn/projects/quick-start-unlocked-packages/update-your-unlocked-package

[wadewegner]

It's incredibly generous of you to take the time to send us this PR. We'll take a look. Thank you, @dseligson!

FYI @ekapner